Processes for alkylating a variety of alkylatable aromatic compounds by contacting such compounds with hydrocarbon radical providing source such as an olefin or alcohol are widely known. Typically, alkylatable aromatic compounds are mononuclear aromatic compounds themselves or those substituted with a hydroxyl, amine or an ether group. The alkylation has been carried out in the presence of homogeneous and heterogeneous catalyst systems.
Ring alkylated aromatic amines have been some of the products produced by alkylation procedures. Ring alkylated aromatic amines have a variety of uses in chemical synthesis. Some of the early uses were intermediates for substituted isocyanates, herbicidal compositions, dyestuffs and textile auxiliary agents. More recently aromatic amines have been utilized as chain lengthening or cross-linking components in polyurethane systems. These are commonly referred to as chain extenders.
Representative references which illustrate some of the early processes in forming ring alkylated aromatic amines are:
British Patent 414,574 discloses the reaction of aniline with various olefins, e.g., cyclohexene and alcohols, e.g., butanol in the presence of a neutral or weakly acidic catalyst system commonly referred to as hydrosilicates at temperatures from 200.degree.-270.degree. C. Ortho and para-cyclohexylaniline, N-cyclohexylaniline, N-butylaniline and para-methyl-ortho-cyclohexylaniline and N-cyclohexyl-para-toluidine are listed as representative products.
British Patent 846,226 discloses ring alkylation of aromatic amines with olefins using active, substantially neutral bleaching earths of the montmorillonite type as a catalyst.
AS 1,051,271 discloses the ring alkylation of aniline with an olefin, e.g., ethylene, in the presence of kaolin or in the presence of aluminum and aluminum alloys. Alkylation with higher olefins, e.g., propylene, butylene, etc., was carried out in the presence of Friedel-Crafts catalysts or bleaching earths under liquid phase conditions at temperatures from 150.degree.-350.degree. C. Examples of catalytic systems included aluminum chloride, zinc chloride, boron trifluoride, sulfuric acid, phosphoric acid and bleaching earth. Ring alkylation at the ortho-position was predominant, although other products such as the di and tri-alkylated aniline product were produced.
In an article by Zollner and Marton, Acta Chim. Hung. Tomus 20, 1959 (Pages 321-329) the vapor phase alkylation of aniline with ethanol was effected in the presence of aluminum oxide.
U.S. Pat. No. 3,649,693 and U.S. Pat. No. 3,923,892 discloses the preparation of ring alkylated aromatic amines by reacting an aromatic amine with an olefin in the presence of aluminum anilide, optionally including a Friedel-Crafts promoter. Reaction products included 2-ethylaniline, and 2,6-diethylaniline.
Stroh, et al., in U.S. Pat. No. 3,275,690; 2,762,845, Japanese Sho 56-110652, and, as mentioned previously, AS 1,051,271, disclose various processes for preparing alkylated aromatic amines by reacting an aromatic amine with an olefin in the presence of Friedel-Crafts catalysts as well as a combination of the Friedel-Crafts catalysts in the presence of halogen compounds combined with aluminum. Representative reaction products included 2-cyclohexylaniline, diethyltoluenediamine, diethylaniline, diisopropylaniline and mono-tert-butylaniline.
The art, e.g., Netherlands Application 6,407,636 has recognized that alkylation of various aromatic and heterocyclic compounds can be carried out in the presence of a zeolite having a pore size from 6-15 Angstroms wherein active cationic sites are obtained with an exchangeable metal or hydrogen cations in their ordered internal structure. Alkylating agents include olefins having from 2 to 12 carbon atoms, alkyl halides such as propylbromide and ethylchloride; and alkanols, such as, methanol, ethanol, and propanol. Various compounds were suggested as being suited for alkylation and these include both the heterocyclic and aromatic ring compounds. For aromatic amine alkylation it was suggested that a zeolite with a disperse distribution of acidic sites should be utilized. It was believed the highly acidic zeolite catalysts which have a high density of acidic sites may bind the amine to the catalyst and block the pore structures. In Example 1 aniline was alkylated with propylene using sodium zeolite X having a pore size of 13 Angstroms and numerous alkylated amines were produced. Example 3 shows alkylation of diphenylamine with cyclohexene using a rare earth exchanged 13 X zeolite. Again, numerous ring alkylated products were produced and high temperatures, e.g. 300.degree. C. and above apparently being required to weaken the amine-acid bond.
French Patent 1,406,739, which is equivalent to Netherlands Application 6,407,636, discloses the preparation of alkylated aromatic compounds having polar substitutions thereon utilizing alumino-silicates having a pore size of at least 6 Angstroms as a catalyst. Cations of low valence were deemed to have been particularly effective for the ring alkylation of aromatic compounds having weakly basic substituents such as aromatic amines. The examples show the alkylation of aniline with propylene in the presence of a sodium zeolite X and alkylation of diphenylamine with propylene in the presence of a molecular sieve 13X which has undergone a partial exchange with rare earths and having a pore size of 13A.degree..
Although the prior art has disclosed that a variety of catalytic systems can be utilized in the alkylation of aromatic hydrocarbons and aromatic amines, the art also teaches that a variety of reaction products are produced, including both ortho and para-isomers of mononuclear aromatic amines as well as, mono, di and tri alkyl substituted amines. In addition the prior art teaches that neutral to weakly acidic catalysts are preferred for effecting ring alkylation of the aromatic amines. Even though the prior art has suggested preferred catalytic systems such systems also involve batch, liquid phase operation which may be difficult to operate over an extended period of time, and tend to give more para product. In addition, many of the processes suffer from poor conversion, poor reaction rate, an inability to produce high ortho to para isomer ratios at high conversion and an inability to produce unsymmetrical amines.